1. Field of the Invention
An exemplary embodiment of the invention relates to a liquid crystal display.
2. Discussion of the Related Art
Active matrix type liquid crystal displays display a moving picture using a thin film transistor (TFT) as a switching element. The active matrix type liquid crystal displays have been implemented televisions as well as display devices in portable devices, such as office equipment and computers, because of the thin profile of the active matrix type liquid crystal displays. Accordingly, cathode ray tubes (CRT) are being replaced by active matrix type liquid crystal displays.
The active matrix type liquid crystal display includes data lines and gate lines crossing each other, and liquid crystal cells arranged at crossings of the data lines and the gate lines in a matrix format. A thin film transistor (TFT) is formed at each crossing of the data lines and the gate lines.
The liquid crystal display periodically inverts a polarity of a data voltage and supplies the inverted data voltage so as to reduce the degradation of liquid crystals. As above, a method for driving the liquid crystal display while the polarity of the data voltage is inverted is called an inversion system. Examples of the inversion system include a line inversion system, a column inversion system, and a dot inversion system.
In the line inversion system, the polarity of the data voltage is inverted every 1 line and is inverted every 1 frame period. In the line inversion system, because the adjacent liquid crystal cells in a line direction are different from each other in the data charge amount, a stripped pattern (i.e., a horizontal stripped pattern) may appear in the line direction.
In the column inversion system, the polarity of the data voltage is inverted every 1 column and is inverted every 1 frame period. In the column inversion system, because the adjacent liquid crystal cells in a column direction are different from each other in the data charge amount, a stripped pattern (i.e., a vertical stripped pattern) may appear in the column direction.
In the dot inversion system, the polarity of the data voltage supplied to the adjacent liquid crystal cells in the line direction is inverted, and the polarity of the data voltage supplied to the adjacent liquid crystal cells in the column direction is inverted. Further, the polarity of the data voltage is inverted every 1 frame period. Because flickers generated between adjacent pixels in vertical and horizontal directions offset each other in the dot inversion system, the dot inversion system can provide more excellent image quality than the line and column inversion systems. However, because the polarity of the data voltage supplied to the data lines has to be inverted in the vertical and horizontal directions in the dot inversion system, the change amount of the data voltage (i.e., a frequency of a data signal) in the dot inversion system is larger than the line and column inversion systems. Therefore, power consumption of a data drive circuit increase, and also the amount of heat generated in the data drive circuit increases.
Recently, as shown in FIG. 1, an inversion system in which data voltages received from one data line are alternately supplied to adjacent liquid crystal cells in a line direction has been proposed. Because a charge path of the data voltages is similar to a Z-shape, the inversion system is called a Z-shaped inversion system. In the Z-shaped inversion system, thin film transistors are formed on left and right sides of each data line, and a pixel electrode of a liquid crystal cell is connected to each thin film transistor.
In the Z-shaped inversion system, when a first gate pulse is applied to a first gate line G1, a first TFT T1 is turned on and the data voltage received from a first data line D1 is supplied to a first pixel electrode PIX1 positioned on the left side of the first data line D1. Sequentially, when a second gate pulse is applied to a second gate line G2, a second TFT T2 is turned on and the data voltage received from the first data line D1 is supplied to a second pixel electrode PIX2 positioned on the right side of the first data line D1. In the same way, when third and fourth gate pulses are sequentially applied to third and fourth gate lines G3 and G4, third and fourth TFTs T3 and T4 are turned on. Then, after the data voltage is supplied to a third pixel electrode PIX3, the data voltage is supplied to a fourth pixel electrode PIX4.
In the Z-shaped inversion system, the number of data lines can be reduced by half, and a frequency of the data voltage can be reduced. However, because the two gate lines are formed between the adjacent pixel electrodes in a column direction, the previously charged data voltage may be changed. For example, when a gate high voltage of the gate pulse is applied to the second gate line G2 in a state where the first pixel electrode PIX1 has been already charged to the data voltage, a voltage level of the first pixel electrode PIX1 may be changed by the coupling between the first pixel electrode PIX1 and the second gate line G2. This reason is that the gate high voltage changes a voltage of a storage capacitor for holding a voltage of the first pixel electrode PIX1 by a short distance Δ1 between the first pixel electrode PIX1 and the second gate line G2. If the distance Δ1 between the first pixel electrode PIX1 and the second gate line G2 increases, the coupling may be reduced, but an aperture ratio may be reduced.
Further, in the Z-shaped inversion system, because the data voltage charged to the liquid crystal cells of one of an R column, a G column, and a B column is different from the data voltage charged to the liquid crystal cells of the other columns depending on a polarity of the data voltage and the charge order of the data voltage, any one color may be seen more remarkably than the other colors on the display image.